The present invention relates to a drivetrain for a hybrid electric vehicle.
In conventional automotive vehicles that include two wheel (rear wheel) drive and four wheel drive configurations, two different transmission configurations are employed-one for the two wheel drive configuration and one for the four wheel drive configuration. The two wheel (rear wheel) drive configuration of the transmission has an output shaft connecting to a U-joint of a drive shaft. The four wheel drive configuration of the transmission has an output end that mounts to an input end of a transfer case, with the output of the transfer case having an output shaft connecting to the U-joint of a shorter drive shaft.
More recently, a desire has arisen to provide hybrid electric automotive vehicles that allow for a two wheel (rear wheel) drive configuration and a four wheel drive configuration. In particular, there is a desire for a hybrid electric vehicle having an internal combustion engine driving a generally conventional transmission, with an electric drive unit downstream in the drivetrain from the transmission. Such a hybrid electric vehicle is desirable in both two wheel (rear wheel) drive and four wheel drive configurations, which can require multiple configurations for the various components in the drivetrain. For example, two different transmission configurations would be needed to accommodate both two and four wheel drive configurations (i.e., without and with a transfer case). And, the electric drive unit needs to be added and connected to the drivetrain in some way. Moreover, some of the underbody systems may need to be modified to allow for packaging of both of these configurations and the extra component. Many of these changes add extra cost and complexity to the various components and to their assembly into the drivetrain.